2007 17", it may be the dreaded Nvidia high lead solder ball issue. That was around the time Nvidia used 90% lead in the solder balls on the video chips. Those are the solder balls between the chip and the substrate, not between the substrate and the PCB.
On several occasions I have heated the die to about 300 ºC for 60 seconds or so. It would then work again, but only for a few months at best.
Just one idea